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A.8.4 The Generic Package Direct_IO

Static Semantics

1
The generic library package Direct_IO has the following declaration: 
2/5
{AI12-0302-1} with Ada.IO_Exceptions;
generic
   type Element_Type is private;
package Ada.Direct_IO
   with Global => in out synchronized
 is
3
   type File_Type is limited private;
4
   type File_Mode is (In_File, Inout_File, Out_File);
   type Count     is range 0 .. implementation-defined;
   subtype Positive_Count is Count range 1 .. Count'Last;
5
   -- File management
6
   procedure Create(File : in out File_Type;
                    Mode : in File_Mode := Inout_File;
                    Name : in String := "";
                    Form : in String := "");
7
   procedure Open  (File : in out File_Type;
                    Mode : in File_Mode;
                    Name : in String;
                    Form : in String := "");
8
   procedure Close (File : in out File_Type);
   procedure Delete(File : in out File_Type);
   procedure Reset (File : in out File_Type; Mode : in File_Mode);
   procedure Reset (File : in out File_Type);
9
   function Mode   (File : in File_Type) return File_Mode;
   function Name   (File : in File_Type) return String;
   function Form   (File : in File_Type) return String;
10
   function Is_Open(File : in File_Type) return Boolean;
10.1/5
{AI12-0130-1} {AI12-0302-1}    procedure Flush (File : in File_Type)
      with Global => overriding in out File
;
11
   -- Input and output operations
12/5
{AI12-0302-1}    procedure Read (File : in File_Type; Item : out Element_Type;
                                        From : in Positive_Count)
      with Global => overriding in out File
;
   procedure Read (File : in File_Type; Item : out Element_Type)
      with Global => overriding in out File
;
13/5
{AI12-0302-1}    procedure Write(File : in File_Type; Item : in  Element_Type;
                                        To   : in Positive_Count)
      with Global => overriding in out File
;
   procedure Write(File : in File_Type; Item : in Element_Type)
      with Global => overriding in out File
;
14/5
{AI12-0302-1}    procedure Set_Index(File : in File_Type; To : in Positive_Count)
      with Global => overriding in out File
;
15
   function Index(File : in File_Type) return Positive_Count;
   function Size (File : in File_Type) return Count;
16
   function End_Of_File(File : in File_Type) return Boolean;
17
   -- Exceptions
18
   Status_Error : exception renames IO_Exceptions.Status_Error;
   Mode_Error   : exception renames IO_Exceptions.Mode_Error;
   Name_Error   : exception renames IO_Exceptions.Name_Error;
   Use_Error    : exception renames IO_Exceptions.Use_Error;
   Device_Error : exception renames IO_Exceptions.Device_Error;
   End_Error    : exception renames IO_Exceptions.End_Error;
   Data_Error   : exception renames IO_Exceptions.Data_Error;
18.1/5
{AI12-0021-1}    package Wide_File_Names is
18.2/5
      -- File management
18.3/5
      procedure Create(File : in out File_Type;
                       Mode : in File_Mode := Inout_File;
                       Name : in Wide_String := "";
                       Form : in Wide_String := "");
18.4/5
      procedure Open  (File : in out File_Type;
                       Mode : in File_Mode;
                       Name : in Wide_String;
                       Form : in Wide_String := "");
18.5/5
      function Name   (File : in File_Type) return Wide_String;
18.6/5
      function Form   (File : in File_Type) return Wide_String;
18.7/5
   end Wide_File_Names;
18.8/5
{AI12-0021-1}    package Wide_Wide_File_Names is
18.9/5
      -- File management
18.10/5
      procedure Create(File : in out File_Type;
                       Mode : in File_Mode := Inout_File;
                       Name : in Wide_Wide_String := "";
                       Form : in Wide_Wide_String := "");
18.11/5
      procedure Open  (File : in out File_Type;
                       Mode : in File_Mode;
                       Name : in Wide_Wide_String;
                       Form : in Wide_Wide_String := "");
18.12/5
      function Name   (File : in File_Type) return Wide_Wide_String;
18.13/5
      function Form   (File : in File_Type) return Wide_Wide_String;
18.14/5
   end Wide_Wide_File_Names;
19
private
   ... -- not specified by the language
end Ada.Direct_IO;
19.a
Reason: The Element_Type formal of Direct_IO does not have an unknown_discriminant_part (unlike Sequential_IO) so that the implementation can make use of the ability to declare uninitialized variables of the type. 
20/2
{AI95-00360-01} The type File_Type needs finalization (see 7.6) in every instantiation of Direct_IO.
20.a.1/2
This paragraph was deleted.{8652/0097} {AI95-00115-01} {AI95-00344-01}

Incompatibilities With Ada 95

20.a/2
{AI95-00360-01} Amendment Correction: File_Type in an instance of Direct_IO is defined to need finalization. If the restriction No_Nested_Finalization (see D.7) applies to the partition, and File_Type does not have a controlled part, it will not be allowed in local objects in Ada 2005 whereas it would be allowed in original Ada 95. Such code is not portable, as another Ada compiler may have a controlled part in File_Type, and thus would be illegal. 

Incompatibilities With Ada 2012

20.b/4
{AI12-0130-1} Corrigendum: The Flush procedure is newly added to Ada.Direct_IO. If an instance of Ada.Direct_IO is referenced in a use_clause, and a procedure Flush is defined in some other package that is also referenced in a use_clause, the user-defined Flush may no longer be use-visible, resulting in errors. This should be rare and is easily fixed if it does occur.
20.c/5
{AI12-0021-1} The Wide_File_Names and Wide_Wide_File_Names nested packages are newly added to Ada.Direct_IO. If an instance of Ada.Direct_IO is referenced in a use_clause, and an entity with one of those names is defined in some other package that is also referenced in a use_clause, the user-defined entity may no longer be use-visible, resulting in errors. This should be rare and is easily fixed if it does occur. 

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